On S&W revolvers, that ring is a fact of life; don't worry about it.
Some revolvers, like the Colt SAA and the old Colt DA's can be timed to drop the cylinder bolt (stop) in the leade (that triangular shaped cut ahead of the stop notch). One reason is that the spring on the bolt on both the SAA and the DA's is very strong and will mar the cylinder if the bolt drops too soon. As a practical matter, that doesn't make any difference, but some users get so worked up that a timing job on those guns usually involves both modifying the drop point and reducing the bolt spring tension.
On most other revolvers (except Colt SAA clones), there is no problem except a purely cosmetic one.